The interest to the DVCS and HEMP reactions is motivated by the fact that
in the Bjorken limit (large \(Q^2\) ), the corresponding amplitudes factorize [1]}, [2]}
in convolution of perturbative (hard) coefficient
functions with nonperturbative (soft) matrix elements,
which are parameterized in terms of generalized parton distributions
(GPDs).
GPDs are universal (process-independent) functions that contain information
on parton distributions, form factors and correlations in hadrons.
GPDs also parameterize parton correlations in
matrix elements
describing transitions between two different hadrons, which appear in
reactions such as
e.g. \(\gamma ^{\ast }p \rightarrow \pi ^{+}n\)  [3]}, [4]}.
